Cryptology ePrint Archive: Report 2017/1044

Strain: A Secure Auction for Blockchains

Erik-Oliver Blass and Florian Kerschbaum

Abstract: We present Strain, a new auction protocol running on top of
blockchains and guaranteeing bid confidentiality against
fully-malicious parties. As our goal is efficiency and low
blockchain latency, we abstain from using traditional, highly
interactive MPC primitives such as garbled circuits. Instead
for Strain, we design a new maliciously-secure two-party
comparison mechanism executed between any pair of bids in
parallel. Using zero-knowledge proofs, Strain broadcasts the
outcome of comparisons on the blockchain in a way such that all
parties can verify each outcome. While Strain leaks the order
of bids, similar to OPE, its core technique of determining the
auction's winner is very efficient and asymptotically optimal,
requiring only 2 blockchain blocks latency. Strain also
provides typical auction security requirements like
non-retractable bids against fully-malicious
adversaries. Finally, it protects against adversaries aborting
the auction by reversible commitments.